During the inspection, you will begin to formulate hypotheses regarding the cause of failure. With these hypotheses in mind, select specimens for laboratory testing. Take broken parts for laboratory evaluation or, if this is not possible, ensure that they will be preserved for later analysis.
Oil samples can be very helpful. But, an effective lubricant analysis depends on how well the sample represents the operating lubricant. To take samples from a gearbox drain valve, first discard stagnant oil from the valve. Then take a sample at the start, middle, and end of a drain to avoid stratification. To sample from the reservoir, draw samples from the top, middle, and near the bottom. Examine the oil filter and magnetic plug for wear debris and contaminants.
Samples from the oil storage drum or reservoir can uncover problems such as excessive water in the oil due to improper storage.